SUBTERRANEAN STEMS. 147 



roots and thickened rhizomes are reservoirs 

 of food supplies for the plant, and these res- 

 ervoirs are drawn upon when the plant has 

 need. Compare the thick, plump tubers or 

 roots of dahlias, potatoes, and turnips as 

 they appear in the fall, with the shriveled 

 remains of these tubers after they have been 

 planted and pumped dry by the growing 

 young plants ; then imagine these plants in 

 a warmer climate where long, dry seasons 

 must be endured, and you can appreciate 

 the importance to the plant of such infalli- 

 ble storehouses. 



The primary office of roots is to supply 

 nourishment to the plant. They always de- 

 mand that this nourishment be dissolved in 

 water. The liquid food is taken into the 

 thin-walled outer cells of the young rootlets 

 by a sort of imbibition process, and it is 

 passed by a similar process from cell to cell. 

 If we were to remove very care- 

 fully from the soil a young plant 

 of Indian corn, or indeed any 

 young plant, and wash it, we 

 should observe a delicate cover- 

 ing like mould upon the young 

 roots. This covering is made up 

 of many minute white hair -like bodies, 



